title: Low-methane yield sheep have smaller rumens and shorter rumen retention time.
abstract: In the present study, following the measurement of methane emissions from 160 mature ewes three times, a subset of twenty ewes was selected for further emission and physiological studies. Ewes were selected on the basis of methane yield (MY; g CH4/kg DM intake) being low (Low MY: >1 sd below the mean; n 10) or high (High MY: >1 sd above the mean; n 10) when fed a blended chaff ration at a fixed feeding level (1·2-fold maintenance energy requirements). The difference between the Low- and High-MY groups observed at the time of selection was maintained (P= 0·001) when remeasured 1-7 months later during digesta kinetics studies. Low MY was associated with a shorter mean retention time of particulate (P< 0·01) and liquid (P< 0·001) digesta, less amounts of rumen particulate contents (P< 0·01) and a smaller rumen volume (P< 0·05), but not apparent DM digestibility (P= 0·27) or urinary allantoin excretion (P= 0·89). Computer tomography scanning of the sheep's rumens after an overnight fast revealed a trend towards the Low-MY sheep having more clearly demarcated rumen gas and liquid phases (P= 0·10). These findings indicate that the selection of ruminants for low MY may have important consequences for an animal's nutritional physiology.
authors.affiliation: Agriculture NSW, Beef Improvement Centre, Trevenna Road, Armidale, NSW 2351, Australia.
authors.forename: John P
authors.initials: JP
authors.lastname: Goopy
authors.affiliation: Agriculture NSW, Beef Improvement Centre, Trevenna Road, Armidale, NSW 2351, Australia.
authors.forename: Alastair
authors.initials: A
authors.lastname: Donaldson
authors.affiliation: School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
authors.forename: Roger
authors.initials: R
authors.lastname: Hegarty
authors.affiliation: School of Animal Biology, University of Western Australia, Perth, WA, Australia.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Vercoe
authors.affiliation: School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
authors.forename: Fay
authors.initials: F
authors.lastname: Haynes
authors.affiliation: School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Barnett
authors.affiliation: Agriculture NSW, Beef Improvement Centre, Trevenna Road, Armidale, NSW 2351, Australia.
authors.forename: V Hutton
authors.initials: VH
authors.lastname: Oddy
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004043:Dietary Fiber / Q000378:metabolism*; D004063:Digestion; D005260:Female; D005772:Gastrointestinal Transit; D017752:Greenhouse Effect; D008697:Methane / Q000378:metabolism*; D012417:Rumen / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D012756:Sheep / Q000378:metabolism*
chemical_list: D004043:Dietary Fiber; D008697:Methane